The overall objectives of this project are the elucidation of primary interactions between viral surface structures (sub-units) and cell receptors leading to viral attachment and transmembranal entry. The reactions of hemagglutinating/hemolytic/fusing viruses with erythrocytes offer models for analyzing these phenomena divorced from stages in replication which follow only in susceptible nucleated cells. Attention is focused on principal transmembranal (glycophorin A, Band III) and peripheral (spectrin, ankyrin) proteins of human and other animal erythrocytes. The viruses which have received most attention are ortho myxoviruses, paramyxoviruses (measles, respiratory syncytial viruses) and herpes simplex viruses.